The present invention relates to filters and, more specifically, relates to filters for placement in the power line of electronic equipment to protect such equipment from damage and/or malfunction.
The problem of power line pollution has become more and more evident as of late. Typically, such power line pollution involves individual transients which are of varying duration and voltage and current surges which ride on top of, or are superimposed onto, the 60 Hz waveform. Such surges or transients represent approximately 90% of the problems in power line pollution, with the other 10% being represented by brownouts and occasional blackouts. Transients may also be called surges, spikes, power bumps, over voltages, over shoots, electrostatic discharge (ESD), and radio frequency interference (RFI).
When power line surges or transients occur that are of sufficient magnitude to cause the electrical equipment to cease functioning, this can be immediately detected. However, modern electronic data processing equipment and other similar sophisticated electronic equipment can be adversely affected by such transients yet still not cease to operate. For example, voltage spikes or transients on the power line may cause memories to read or write ones instead of zeroes, to affect adversely the central processing unit, and to disrupt the input/output bus and controller regulating circuitry, all of which can ultimately cause error, data loss, or disruption of the priority interrupt system. Thus, the effects of these low-level transients are oftentimes more serious and insidious than simply dropping out the over-voltage protector, i.e., opening the main power circuit breaker. It has now been learned that such low-level transients are actually responsible for many apparently unexplained or random failures in electronic data processing equipment.
The power companies supplying power have altered their power grid networks in order to overcome the brownout and blackout problem; however, since computers and other sensitive electronic equipment represent less than 0.01% of the total national power load, the utility companies do not view the problems discussed as major, since the present power quality is certainly adequate for conventional electrical equipment such as lights, heaters, motors, and the like. Ironically, it is this conventional electrical equipment whose operation adversely affects the power being fed to the computers and other complex electronic equipment. Fluorescent lighting, copiers, teletype equipment, and paging systems all place demands upon the power system which can create unwanted and undesirable power line transients. Additionally, in the past, electrical equipment was turned on and off by means of simple switches, but today the use of electronic or solid-state devices has become very popular. While replacing electromechanical devices with solid-state devices has its advantages, there are also severe disadvantages. Specifically, extensive voltage spikes are generated by these electronic switches. For example, one need only monitor the output voltage of an SCR type elevator controller to see the extent of these voltage spikes. These spikes adversely affect almost all types of sensitive electronic equipment. Moreover, computers themselves, as well as computer peripherals, can generate transients and transient noise, which can contaminate the power line. This then can create problems for the other electronic equipment on the line.
These problems are of such magnitude that several European countries have promulgated regulations regarding the generation of transients by computers and their peripherals. More recently, the Federal Communications Commission has also set forth rules limiting the extent to which computers, electronic games, and other electronic devices may pollute the power lines and, thus, create interference inimicable to radio communications.
With the vast majority of complex electronic equipment using not only transistors but also integrated circuits, and with such integrated circuits now being constructed with large scale integration (LSI), this problem has achieved major proportions. This is particularly true, since most fast rise-time, short-duration transients contain a high-frequency spectra to which transformers, motors, heaters, lights, vacuum tubes, and electromechanical instruments are relatively immune but which are anathema to modern solid-state electronic equipment. The integrated circuit devices are generally safe from any damage by such fast rise-time, short-duration transients, but the high frequency spectrum frequently disrupts the operation of the device.
Accordingly, there exists a need to provide clean power to complex data processing equipment in order to preclude equipment damage, as well as to prevent any malfunctioning of the equipment.